“…For example, Sun and Kalbfleisch (1995), Wellner and Zhang (2000), Zhang and Jamshidian (2003), Lu et al (2007), and Hu et al (2009a) studied nonparametric estimation for the mean function of the counting process with panel count data; Thall and Lachin (1988), Sun and Fang (2003), Zhang (2006), and Balakrishnan and Zhao (2009) proposed some nonparametric tests for the problem of nonparametric comparison of treatment groups based on panel count data. Sun and Wei (2000), Cheng and Wei (2000), Hu et al (2003), and Hua and Zhang (2012) discussed regression analysis of panel count data by the estimating equation-based approaches, while Zhang (2002), Wellner and Zhang (2007), and Lu et al (2009) presented more efficient inference procedures for joint estimation of parametric and nonparametric components in the proportional mean model by the likelihood-based approaches. In addition, Huang et al (2006) and Sun et al (2007) considered the analysis of panel count data with informative observation times.…”